During a scheduled semi-weekly contact on Friday, May 3, 2013, engineers discovered that the Kepler spacecraft was in a self-protective state called a safe mode. The spacecraft was returned to science data collection just before midnight on Monday, May 6, 2013.
The spacecraft entered thruster-controlled safe mode at about 7:30 p.m. PDT on Wednesday, May 1, 2013. The recovery operation began at about 5 p.m. PDT on Friday, May 3, 2013, after engineers had verified that the spacecraft was otherwise operating normally. The spacecraft responded well to commands and transitioned from thruster control to reaction wheel control as planned.
Following the safe mode recovery, the team performed a routine monthly data downlink from the on-board solid-state recorder on May 5, 2013, and returned to science data collection. The monthly download was originally scheduled for May 8-9, 2013.
The root cause of the safe mode is not yet known but the engineering team is analyzing the data set downloaded during the monthly contact. The reaction wheels do not appear to be the cause of the safe mode. Early indications suggest anomalous star tracker performance. The loss of science data is estimated to be about five days.
Due to mandatory, across-the-board reductions in the Federal budget – termed "sequestration" – which went into effect on March 1, 2013, the team is reassessing plans to host the second Kepler Science Conference at NASA Ames Research Center. The conference had been scheduled for November 2013.
Updates on the safe mode and the Kepler Science Conference will be provided as additional information is available.